Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.006C.

Section : Dead animals.

This refers to animals which die from “natural causes,” that is, without the proper Islamic way of slaughtering. It also includes anything that is cut off of a live animal. Abu Waqid al-Laithy reported that the Prophet, upon whom be peace, said, “What is cut off of a live animal is considered dead,” i.e., it is considered like an animal that has not been properly slaughtered. This is related by Abu Dawud and by at-Tirmizhi, who classifies it as hassan and says that the scholars act according to this hadith.